Bouke

Hi everybody,
I'm new on this forum, dutch from origine and living in Romania., I have some friends here driving Cherokees and always asking me to resolve electric problems. Usually I manage but this time I'm having some difficulties I can't get my finger on:
So the case is a XJ 2.5 diesel that doesn't charge anymore. The car was brought to someone who messed around with it and now the charging problem is still there but I have additional issues on top of that: The glow plug relay doesn't do it anymore and it is not the relay itself, the shut-off valve on the mechanical injection pump (replaced, originally it was electric) is not activated anymore and a 20A fuse keeps on blowing out. The next picture is to give you guys an overview of the engine we are talking about:

So the fuse that keeps on blowing out is shown on the next picture:

Anybody have an idea? What does this fuse exactly protect?
But my main question: Why ain't it charging anymore. So I had at my disposition an exact same Cherokee and I took the different parts out and tested them in this good working car. Both the boxes, under the steering wheel and in the engine bay, the alternator... everything works fine in the other car. I checked the 2 wires going to the alternator, they are okay. Massa connection between alternator and battery is okay. So could there be a sensor or so not allowing the field of the alternator to be powered? I tried to get information about the temp sensor (Mopar pn 56041053) under the battery but don't get the resistor value of it. The company making them doesn't give me any useful information.
I already passed 2 full days on this car and I'm running out of ideas.
Really would appreciate some input here.
Thank you in advance and if more information is required, please let me know.
Bouke

Saudade

You can go to Cruiser54's site here: https://cruiser54.com/?page_id=365 and get the 2000 FSM.

The diagram for the 2.5 Diesel Power Distribution Center indicates that fuse (Fuse #21) powers the glow plug relay, fuel injection pump, and the electric vacuum modulator. It also provides the "fused Auto Shutdown Relay Output to the PCM which appears in the charging system diagrams but seem to apply only to the gas engines. So I'm not sure that it affects your charging circuit directly.

There is a battery temperature sensor so I'd check that too. The FSM will give procedures for testing.

Bouke

Hi Saudade,
thank you for your reaction. Of course, I immediately downloaded the pdf of 2119 pages () and already started studying and have some questions:
Where did you find the fuse 21 in the pdf? I have been looking in the 8W-20-4 'charging system diesel' page 733 and the 8W-21-6 'starting system diesel' page 741 but there I don't find this fuse.
And I did find the batt temp sensor but not where it sais how to test it. Could you give me some page numbers here?
Thank you in advance and have a nice day.
Bouke

Saudade

The box with fuses in the engine bay is the Power Distribution Center (PDC). Section 8W (Wiring Diagrams) Page 8W-10-7 is the layout for the Diesel. That spot is Fuse 21. Once open in Acrobat (or whatever PDF tool you use), you can use the text search for "fuse 21" (without the quotes) and find all the locations that call it out.

Page 8W-10-34 shows the fuse and the connections to the relays.

Just make sure you're looking at Fuse 21 in the PDC and not the Junction Block (JB, under the dash). Also make sure you're looking at the Diesel pages and not the Gas (Petrol) pages.

Page 8W-20-4 Charging System Diesel wiring diagram and does not show Fuse 21 playing here. Doesn't mean there's not a short somewhere that may affect it.

Section 8C is the charging system with the diagnostics.

Since this FSM is in parts, file EXJ_TAB.PDF is the "table of contents:". You can click on any tab and it should open the appropriate section.

Is your Check Engine light on? If so, can you read the codes?

Bouke

Hi Saudade and other readers,
Sorry it has been a while but had some other things on my plate. So I resolved the problem with fuse 21: short circuit of 2 wires going to the fuel pump. The pre-heating plugs work again and the fuse doesn't blow anymore. Remains the fact that the fuel valve (white black wire, only got 2.5V on that lead coming in as a bleu/black line wire)

on the pump doesn't open with the contact put and the alternator isn't charging so I presume fuse 21 hasn't anything to do with that as you already said you thought. As said in my former post, I exchanged both cdi units (under the steering wheel and engin compartment) and the alternator with a similar Cherokee and in that car everything works fine. Also, in that car the battery temp sensor was taking out but the alternator stil charges the battery so I presume a faulty sensor can't be the problem neither. Never got the resistor value of this sensor so I can't put a resistor in place to overrule the sensor to see if this solves my ploblem. No Check Engine light on in the dashboard.
Really gonna need expert inside here
Thanks in advance again for your input or everybody else's remarks.
Bouke.